H01H13/00—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch

H01H13/70—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard

Abstract

The assembly has a resilient keycap 2 which is arranged in use to project through an aperture through an outer surface of a keyboard and located so as to extend just proud of the outer surface. A flange 10 around the keycap extends radially outwardly from the keycap to limit the amount of projection of the keycap 'U through the aperture and to engage a waterproof rubber membrane stop 5 on the keyboard to prevent undue travel of the keycap inwardly into the keyboard. A resilient buffer 3 is located in a concave cavity within the keycap. The buffer is movable by the keycap until the keycap flange 10 engages the stop 5 and continues to be moved to operate a switch 1 mounted on the keyboard by the keycap being movable inwardly so that the buffer member absorbs compressive forces and undue tolerances when operating the switch of the keyboard. The keycap assembly enables the construction of a rugged keyboard which is waterproof, robust and less likely to be rendered inoperative by abuse from vandals and is suitable for use with kiosks which may be located indoors or outdoors.

Description

<tb> Field <SEP> of <SEP> Invention
<tb>
This invention relates to improvements in or relating to keyboards, and more specifically to keyboards which are for public use both indoors and outdoors at public computerised terminals.

State of the Art
It is well known to locate computer type terminals available for public use at bus, rail, or air terminals, car showrooms, post offices, libraries, etc. to enable the public easy access to information services and/or the internet.

It is a particular requirement of such keyboards, particularly when located in the open air, to be both waterproof and very strong or rugged to minimise the effect of the weather, heavy handed use by the public, or abuse by vandals.

The risk of damage has been minimised by providing keyboards in which each individual keycap of the keyboard is arranged to lie flush with the outer keyboard surface or to be recessed to avoid the keycaps being banged and subsequently damaging a switch which lies directly beneath each keycap.
Nevertheless, such keyboards remain susceptible to damage, not only by vandals, but also because their operation can be affected by component parts of the keycaps being on their outer limit of manufacturing tolerances. In this latter instance there is much less tolerance to abuse and the switches beneath
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With <SEP> the <SEP> current <SEP> trend <SEP> also <SEP> to <SEP> minimise <SEP> the <SEP> overall <SEP> thickness <SEP> of <SEP> the
<tb> keyboard the one solution during manufacture would be to choose switches of the individual keys which have a very small length of travel of the switch when operated resulting in a switch body of reduced size to those currently in use.

One particular form of switch which may be used has an operating travel of 0.4 mm to operate the switch between on and off states. However, the manufacturing tolerances of the remaining parts surrounding the switch and through which the switch is operated, particularly the keycap assembly, can result in an effective reduction in the travel of the switch by : to. 20 mm or more, thereby rendering the switch ineffective because it either cannot be operated or it will operate only over a relatively small part of its full movement. Consequently, the switch will not be 100% effective and could be readily open to the problems mentioned above.

Some manufacturers have sought to overcome this problem by providing switches having an operating length of as much as 1.4 mm with the switch operating to either close or open its contacts within the last 0.4 mm of the travel of the operating element of a switch.

One known form of switch having an operating travel of 1.4 mm has a ball and spring arrangement immediately beneath an aluminium plate which is fixed relative to a disk defining a keycap which in turn is arranged to lie flush with or recessed within an outer face of a keyboard. Manufacturing
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<tb> tolerances <SEP> on <SEP> the <SEP> aluminium <SEP> plate <SEP> and <SEP> keycap <SEP> disk <SEP> can <SEP> easily <SEP> render <SEP> the
<tb> operating <SEP> travel <SEP> of <SEP> the <SEP> disc <SEP> to <SEP> be <SEP> reduced <SEP> by <SEP> 0. <SEP> 5 <SEP> mm <SEP> and <SEP> in <SEP> such <SEP> a <SEP> case <SEP> the
<tb> switch is liable to become severely damaged by operators pushing unduly hard upon the keys of the keyboard because the keycap may be only partially depressed while the switch has completed its movement and further pressure upon the keycap can break the switch.

It is an object of the present invention to provide a keycap assembly for a switch in which the above mentioned difficulties are substantially alleviated.

According to one aspect of the present invention there is provided a keycap assembly for an electronic keyboard, comprising a keycap and buffer member of a resilient material for absorbing compressive forces when used for operating a switch of the electronic keyboard.

In one preferred embodiment in accordance with the present invention the keycap may have a recess for receiving the buffer member therein and a domed roof defining a closed end of the roof as well as a contact surface for pushing the key in use.

The keycap conveniently has a flange extending outwardly from a side or sides thereof.

In an alternative embodiment the buffer member includes a protruding member for engaging the switch.

Preferably, the buffer member includes a further protruding member extending from an opposed surface of the buffer member to that from which the first mentioned protruding member extends. The opposed surfaces of the
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Conveniently, <SEP> the <SEP> protruding <SEP> member <SEP> can <SEP> be <SEP> a <SEP> hemispherical
<tb> protrusion, with the further protruding member preferably a cylindrical protrusion.

In another embodiment the cylindrical protrusion is arranged to be located inside the recess of the keycap against the closed end thereof and the hemispherical protrusion extending outwardly from the recess.

Conveniently, a body of the buffer member lies in the recess flush with an open outer edge of the keycap, the hemispherical protrusion extending outwardly beyond its open outer edge of the keycap.

Preferably, one protrusion may be provided on each of two opposed sides of the buffer member. A plurality of such protrusions can be provided on each of the two opposed sides of the buffer member, particularly in the instance where the keycap assembly is of an elongate rectangular configuration.

Preferably, where the keycap assembly is of a square shaped
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<tb> 2
<tb> configuration, <SEP> say <SEP> 1. <SEP> 5 <SEP> cm, <SEP> there <SEP> is <SEP> only <SEP> one <SEP> protrusion <SEP> on <SEP> each <SEP> opposed <SEP> side
<tb> of the buffer member. When the keycap assembly is say 1.5 cm by 3.4 cm two protrusions can be provided on each of the two opposed sides of the buffer member. When the keycap assembly is say 1.5 cm by 11 cm then three protrusions may be provided on each of the two opposed sides of the buffer member.

In accordance with another aspect of the present invention there is
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Conveniently, <SEP> the <SEP> mass <SEP> of <SEP> thermoplastic <SEP> rubber <SEP> material <SEP> is <SEP> a <SEP> sheet <SEP> of
<tb> such material. Preferably, the sheet has a protrusion on each opposed side thereof. One protrusion may be of a cylindrical configuration, with the other protrusion preferably being of a hemispherical configuration.

In accordance with a further aspect of the present invention there is provided a keyboard comprising a plurality of keycap assemblies as mentioned above in accordance with the present invention.

Brief Description Of Drawings
Embodiments of the present invention will now be described by way-of example with reference to the accompanying drawings, in which :
Figure 1 is a cross sectional side elevational view of a keycap assembly and switch of an electronic keyboard;
Figure 2 is a side elevational view of one keycap assembly together with its insert;
Figure 3 is a side elevational view of a second keycap assembly;
Figure 4 is a side elevational view of yet another keycap assembly; and
Figure 5 is a top view of one form of kiosk keyboard.

Description of Embodiments
Referring specifically to Figure 1 there is shown generally a switch assembly which is one switch assembly of a plurality of such switch
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A keycap assembly comprising keycap 2 and insert 3 is located directly above the switch 1. The keycap assembly and switch 1 are separated one from the other by a waterproof silicone rubber membrane 5 extending over the whole of the area of a keyboard such as shown in Figure 5, to ensure the switches are protected against the ingress of liquids inadvertently or intentionally poured over the keyboard and keys.

The keycap 2 shown in Figure 1 is of a square shaped configuration (13 mm x 13 mm), when viewed from above in the direction of arrow 6 and has an outwardly directed domed top operating surface 7. Opposed inner surface 8 to the operating surface 7 correspondingly defines a"domed"recess 4.

The keycap 2 has very short side walls 9 and radially outwardly extending flanges 10 perpendicular to the sidewalls 9, which are of a length sufficient to prevent removal of the keycap 2 by vandals because the flanges 10 are trapped beneath face plate 15 of the keyboard.

Insert 3 is located within the recess 4. The insert 3 has a square shaped configuration corresponding in size to the internal dimensions of the recess 4 and is an interference fit with the recess 4. When located within the recess 4 outer surface 15 of the insert is arranged to lie flush with the flanges 10.

Since the inner surface 8 of the keycap 2 is domed, innermost surface 17 of the insert 3 does not engage the inner domed surface 8 and therefore a flat
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A hemispherical extension 19 projects outwardly from outer surface 16 of the insert in an opposite direction to the projection of the extension 18, and towards free surface 20 of an enlarged diameter portion 21 of an elongate plunger 22 for operating switch 1.

The enlarged diameter plunger portion 21 is located directly beneath the membrane 5 in an aperture 23 of an apertured stop plate 24 which also serves to clamp the membrane 5 against the face place 15. However, although the membrane 5 is held tightly between the face plate 15 and stop plate 24 there is sufficient resilience within the membrane to allow the insert 3 to push the plunger 22 downwardly to operate switch 1.

The switch 1 is fixed to a printed circuit board 25 by soldering of contacts of the switch to the circuitry (not shown) on the printed circuit board.

The switch 1 mounted on to printed circuit board 25 is spaced from the stop plate 24 and the plunger 22 of the switch 1 is movable in a vertical direction up and down with a maximum movement of 0.40 mm between the on and off conditions of the switch. The switch incorporates a stop which limits the maximum normal downward movement of the plunger 22.

In operation of the keycap, when a person using the kiosk keyboard presses on the top of a keycap, the keycap moves downwardly pushing down on the insert. The hemispherical extension 19 engages the membrane slightly displacing the membrane 5, and forcing the plunger 22 downwardly to operate
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<tb> the <SEP> switch <SEP> 1. <SEP> Undue <SEP> movement <SEP> of <SEP> the <SEP> key <SEP> may <SEP> cause <SEP> the <SEP> plunger <SEP> to <SEP> be <SEP> moved
<tb> downwardly <SEP> against <SEP> the <SEP> stop <SEP> plate <SEP> 24. <SEP> The <SEP> flange <SEP> 10 <SEP> of <SEP> the <SEP> keycap <SEP> 2 <SEP> engages
<tb> the stop plate 24 through the membrane 5 thereby providing mechanical overtravel protection for the keycap 2. The insert 3, being of a resilient thermoplastic rubber, compresses as the plunger 22 hits its internal stop so that any further compressive force applied upon the plunger by further movement of the keycap downwardly is buffered by the resilience of the material of the insert 3.

In this way complete protection of the switch is provided for any undue depression of the keycap. Furthermore, excessive tolerances in the manufacture of the device can be taken up by the compressive nature of the insert 3.

Keycap 2 and insert 3 shown in Figure 2 is similar to that shown in
Figure 1. Keycap 2 and insert 3 shown in Figure 3 represents the return key of the keyboard, which has a width of approximately 2Y2 times that of the smaller keys of Figure 2. The insert in this instance has two spaced hemispherical projections 19 on its lower surface and two spaced cylindrical extensions 18 on its upper surface, each hemispherical extension being associated with a switch 1, respectively. The two switches have the same function but enable pressure applied to anywhere on the elongate keycap 2 to be translated into the required command.

A ridge 26 extends between the two spaced cylindrical extensions 18 in
Figure 3 and extends outwardly from the body of insert 3 by the same amount
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<tb> as <SEP> each <SEP> cylindrical <SEP> extension <SEP> 18. <SEP> Therefore, <SEP> the <SEP> ridge <SEP> 26 <SEP> also <SEP> engages <SEP> the
<tb> under <SEP> surface <SEP> of <SEP> the <SEP> keycap <SEP> 2 <SEP> to <SEP> provide <SEP> a <SEP> more <SEP> even <SEP> feel <SEP> to <SEP> say <SEP> the <SEP> return
<tb> key when pressing the keycap at either end or side thereof.

The keycap shown in Figure 4 represents the space bar of the keyboard and in this instance has three spaced hemispherical extensions 19 on the lower surface of the insert and three opposed cylindrical extensions 18 on the upper surface of the insert. As in the embodiment in Figures 3, each of the hemispherical extensions is associated with a switch 1 so that in Figure 4 there are three associated switches 1 of the type described in Figure 1. Each of the switches 1 will operate to perform the same functional command irrespective of where the space bar is pressed.

Again the ridge 26 is provided between each adjacent pair of spaced cylindrical extensions 18 to provide an even feel to the elongate key when pressing the keycap at either end, centre or side thereof.

The keyboard shown in Figure 5, which is eminently suitable for use in a kiosk, preferably has a stainless steel faceplate 15 with stainless steel keycaps 2 for each of the individual switches of the keyboard. Each of the keycaps is arranged to project above the faceplate 15 and the flanges 10 of each keycap are sufficiently wide to prevent the keys from being prised from the keyboard. The raised keycaps and the doming of the keycaps relative to the outer surface of the faceplate provides a more effective feel of the keycaps by an operator's fingers and also allows for the pressure to be applied more evenly to the key when applying pressure from the side of the keys. Because
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To complete the keyboard there is provided a rotational ball 27 located at the right hand end thereof. The ball 27 functions as a traditional computer mouse to move the cursor around the screen in a known manner. The ball device is of a known construction and in a standard form, and is not part of the present invention so will not be further described herein.

Therefore, there has been provided a waterproof, strong and very robust keyboard ideally suited for use with kiosks of the type which are located indoors or outdoors and are permanently available to the public and open to abuse by vandals. Because of the construction of the key assembly no damage will be transmitted to the switch even when very severe blows are applied to the keys.

The keyboard and keycaps are made of metal, preferably stainless steel because this is the most resistant of metals. However, it is conceivable there would be applications where lesser materials can be used, even hard plastics materials.

In addition, although the keys of the keyboard have been described herein with reference to keycaps of a rectangular configuration, it will be clear the keycaps can be of any shape, such as circular for example.

The extentions 18 described above as being cylindrical may have any suitable cross-section such as circular, rectangular, triangular, trapizoidal, etc.
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<tb>

Therefore, <SEP> there <SEP> has <SEP> been <SEP> described <SEP> a <SEP> keycap <SEP> assembly <SEP> which <SEP> enables
<tb> the <SEP> constructions <SEP> of <SEP> a <SEP> keyboard <SEP> which <SEP> is <SEP> waterproof <SEP> and <SEP> much <SEP> stronger <SEP> and
<tb> robust <SEP> then <SEP> currently <SEP> known <SEP> keyboards <SEP> and <SEP> is <SEP> considerably <SEP> less <SEP> likely <SEP> to <SEP> be
<tb> rendered <SEP> inoperative <SEP> by <SEP> abuse <SEP> from <SEP> vandals.
<tb>

Claims (24)

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<tb>

CLAIMS <SEP> :
<tb>
<img class="EMIRef" id="024181889-00120002" />

<tb> 1. <SEP> A <SEP> keycap <SEP> assembly <SEP> for <SEP> an <SEP> electronic <SEP> keyboard, <SEP> comprising <SEP> a
<tb> keycap and buffer member of a resilient material for absorbing compressive forces when used for operating a switch of the electronic keyboard.

2. An assembly as claimed in claim 1, wherein the keycap has a recess for receiving the buffer member therein.

3. An assembly as claimed in claim 2, wherein the keycap has a domed roof defining a closed end of the recess.

4. An assembly as claimed in claims 1,2 or 3, wherein the keycap has a flange extending outwardly from a side or sides of the keycap.

5. An assembly as claimed in any preceding claim, wherein the buffer member includes a protruding member for engaging the switch.

6. An assembly as claimed in claim 5, wherein the buffer member includes a further protruding member extending from a surface of the buffer member opposed to that from which the first mentioned protruding member extends.
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8. An assembly as claimed in claim 6, wherein the opposed surfaces of the buffer member are parallel surfaces.

9. An assembly as claimed in any of claims 5 to 8, wherein the switch engaging protruding member is a hemispherical protrusion.

10. An assembly as claimed in claim 9, wherein the cylindrical protrusion is located inside the recess of the keycap against the closed end thereof and the hemispherical protrusion extends outwardly from the recess.

11. An assembly as claimed in claim 10, wherein the buffer member lies in the recess flush with an open outer edge of the keycap, the hemispherical protrusion extending outwardly beyond the open outer edge of the keycap.

12. An assembly as claimed in claim 10 or claim 11, comprising only one said protrusion on each of two opposed sides of the buffer member.

13. An assembly as claimed in any preceding claim, wherein the keycap is of a square-shaped configuration.
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21. <SEP> An <SEP> assembly <SEP> as <SEP> claimed <SEP> in <SEP> any <SEP> one <SEP> of <SEP> claims <SEP> 16 <SEP> to <SEP> 20, <SEP> wherein <SEP> a
<tb> support <SEP> ridge <SEP> extends <SEP> between <SEP> each <SEP> pair <SEP> of <SEP> adjacent <SEP> protrusions <SEP> on <SEP> that <SEP> side
<tb> of the buffer member arranged to face the internal surface of the keycap.

22. A keyboard comprising a keycap assembly as claimed in any of the preceding claims.

23. A keycap assembly substantially as hereinbefore described with reference to, or as illustrated in, Figure 1; Figures 1 and 2; Figures 2 and 3; or
Figures 1 and 4 of the accompanying drawings.

24. A keyboard substantially as hereinbefore described with reference to, or as illustrated in Figures 1 and 5; Figures 2 and 5; Figures 3 and 5;
Figures 4 and 5; or Figure 5 of the accompanying drawings.